HAL-BRGM, les publications scientifiques en libre accès du BRGM
Not a member yet
14098 research outputs found
Sort by
Assessing soil health at former thermal power plant sites through a functional approach
No full textInternational audiencePurposeSoils resulting from industrial activities are often perceived as severely degraded. However, they can exhibit unexpected and largely unexplored diversity in terms of soil health. This study aimed to assess soil health at two former thermal power plants based on soil characteristics (physical, chemical and biological properties) using a functional approach and a semi-quantitative rating method.MethodAt each site, areas corresponding to different previous industrial uses were identified, with the selection of twelve 100 m2 plots that were homogeneous in terms of vegetation and soil and distinct from each other. Within each plot, a soil profile was dug, described, sampled and analysed for bio-physico-chemical parameters. A dedicated model was applied to score soil functions from a selection of explicit parameters.ResultsEvaluation of the twelve soil profiles highlighted a strong heterogeneity, reflecting contrasted past land uses and soil modifications. Even soils sharing similar land uses differed markedly in terms of soil morphology, physicochemical and biological properties. Functional scores ranged from 0.25/5 to 3.96/5, revealing different potentials as far as carbon storage, biodiversity reservoir, water regulation and plant support functions are concerned. Overall soil health ranged from “strongly degraded” to “good”, with no soil reaching the “very good” class.ConclusionA soil health assessment, based on a multi-parameters functional approach, was conducted on two former thermal power plant sites. An original scoring method was developed that revealed a wide diversity in soil health levels that was explained by: i) pedoclimatic conditions, ii) past land uses and iii) management practices. Despite human impact, some Technosols showed relatively good soil health, confirming the hypothesis that high anthropization is not straightforwardly correlated to the level of soil functions
Permeability impairment by hydrodynamic pore bridging: Probabilistic pore-network modeling and microfluidic experiments
No full textInternational audiencePermeability impairment caused by the migration and retention of suspended particles is a critical issue in numerous industrial and environmental processes. While pore-network models (PNMs) have successfully described clogging by sieving and particle aggregation, they have failed to capture hydrodynamic bridging -a mechanism where particle arches form and block pore throats. This study introduces a novel probabilistic PNM that incorporates a stochastic law for arch formation, accounting for the particle-to-throat size ratio, particle concentration, and pore geometry. The probability law is calibrated using high-fidelity CFD-DEM simulations of single-pore bridging. Microfluidic experiments in heterogeneous micromodels representative of the rock microstructure are carried out to investigate the effect of particle size and concentration, and flow rate on permeability reduction. The proposed probabilistic framework successfully reproduces experimental trends in clogging dynamics and permeability decline, thereby extending the capability of PNMs to capture all three pore-clogging mechanisms
High-Resolution Facies Characterization and Metre-Scale Depositional Organization of Palustrine-Lacustrine Carbonates
No full textAccurate 3D modelling of continental limestone reservoirs is still hindered by the high spatial variability of their flow properties. This variability results from the combination of heterogeneous and laterally discontinuous sedimentary facies with vertically stacked pedogenic overprints, which remain poorly constrained at the multi-meter scale. To address this issue, this study provides a sedimentological and stratigraphic characterization of the Aquitanian Pithiviers Limestones hosting the vadose zone of the Beauce aquifer (central France). This analysis takes advantage of a high-resolution dataset (eight 25-m-deep cored boreholes, spaced 5 to 8 m apart). Eleven facies were identified grouped into lacustrine, lake-margins and palustrine depositional environments. Two cross-sections (22 m long) reveal a heterogeneous architecture structured by three hierarchical orders of cyclicity: (1) medium-term cycles (several metres thick) record alternations between widespread lacustrine and palustrine conditions, (2) short-term cycles that document vertical and lateral facies shifts at the metre scale and (3) very-short-term cycles illustrating sub-metre to metre-scale facies variability driven by autogenic processes. Palaeogeographical reconstructions highlight three depositional organizations: lacustrine-dominated, palustrine-dominated, and mixed configurations. Mixed configurations exhibit pronounced spatial heterogeneity, with lacustrine, lake-margins, and palustrine facies coexisting laterally at the scale of the study site, over distances of a few metres. Lake-margins deposits are restricted in extent and frequently absent from vertical successions, indicating rapid pedogenic overprinting. These results demonstrate that autogenic processes dominate metre-scale facies architecture in lacustrine–palustrine carbonate systems and must be explicitly accounted for when modelling fluid flow and connectivity in continental carbonate aquifers
Three-dimensional geoelectrical imaging beyond 1 km depth for mineral exploration: framework of deep electrical resistivity tomography and induced polarization with advanced strategies
No full textInternational audienceDirect current electrical resistivity tomography (ERT) is a widely used geophysical method for near-surface investigations, offering high-resolution imaging for geological, engineering and environmental applications. While traditional ERT surveys typically target depths of 0-200 m, technological advancements have enabled deeper investigations, commonly referred to as Deep ERT. In this study, we explore the practical challenges and methodological improvements associated with Deep ERT, particularly when combined with induced polarization (IP) measurements. Rather than other electromagnetic methods, ERT offers a more straightforward framework for analysing IP effects, which can potentially correlate with the volume fraction of ore minerals. Nevertheless, deep IP investigations are often challenged by weak signal strength and various sources of electromagnetic interference. To address these challenges, we evaluated key strategies including survey planning, high-power current injection, unconventional electrode configurations and advanced signal processing techniques. The adoption of nodal geophysical recording systems eliminates the logistical constraints of cabled multi-electrode setups, improving flexibility and data acquisition efficiency. Additionally, continuous full timeseries recording allows for enhanced noise filtering and signal stacking, ultimately increasing the signal-to-noise ratio and extending the effective exploration depth. We demonstrate this methodology through a comprehensive case study conducted at the Koillismaa Linear Intrusion Complex in Finland, where a 3-D Deep ERT-IP survey successfully delineated conductive and chargeable anomalies at depths exceeding 1.5 km. These anomalies closely align with independent gravity and borehole logging data, consistent with the mafic-ultramafic intrusion structures. Our results emphasize the importance of balancing data quality, survey efficiency and spatial resolution in survey design. This work not only provides a robust workflow for the implementation of Deep ERT-IP surveys but also represents the first documented successful acquisition of high-quality IP data at these substantial depths, significantly advancing the state of deep geoelectrical exploration
Balancing stability and flexibility in climate crises governance: Lessons from Brazil's water sector
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/616266/) * Autres projets (id;sigle;titre): 16–2014 ODISSEIA;;(BRA) INCT ODISSEIA//International audienceClimate-induced crises such as droughts and floods increasingly strain public institutions, particularly where authority is fragmented and decisions must be made under urgency and uncertainty. This article examines Brazil's river-basin monitoring rooms as procedural instruments of water crisis governance. Adopting a pragmatist lens that links practical authority and policy instrumentation, we analyze two cases—São Francisco and Paraíba do Sul—using a qualitative, multi-source research design. We show that monitoring rooms enable flexible, real-time coordination by combining technical forecasting with structured, bounded deliberation. Their authority is built in practice through recurrent mechanisms: problem-solving under uncertainty, translation of hydrological and energy data into accessible terms, and sustained relational work that supports trust and compliance. Monitoring rooms complement basin committees by bridging urgent crisis response with longer-term governance, and they have become institutionalized through repeated crisis use. The discussion situates these findings within collaborative governance and policy instrumentation debates, and highlights how similar procedural arenas in other domains (e.g., wildfire or pandemic response) can make governance more workable under stress
Mesoproterozoic orogeny in Malawi, part 1: Irumide Domain
No full textInternational audienceThe Mesoproterozoic Irumide belt is a paired orogen comprising two contrasting segments. The northerly, Irumide Domain, is composed of reworked Palaeoproterozoic crust and Mesoproterozoic igneous rocks. To the south, the South Irumide Domain consists of an assembly of juvenile Mesoproterozoic arc-related crustal blocks. The suture between the two domains is a sharp tectonic contact marked by a sudden change in lithologies, magmatism and isotopic signature. This paper describes the northern segment where recent geological mapping and laboratory studies allow its precise delineation in Malawi, building upon the definitions established in adjacent Zambia and Mozambique. The Irumide Domain has been subdivided into the Mzimba, Kasungu and Mchinji subdomains. Each contains high-grade paragneisses that post-date the ∼2 Ga Ubendian orogeny. Two age-sequences are recognized; an older assemblage of paragneisses and quartzites considered to be high-grade metamorphic equivalents of the Muva Supergroup in Zambia, and including the Mafingi Group in Malawi. Detrital zircon data show that the other paragneiss sequence also contains significant contributions of ∼1100 Ma source rocks currently unknown from Zambia. These younger paragneisses, together with a suite of granitoid orthogneisses dated at ∼1080 Ma, provide evidence for a short-lived Mesoproterozoic active continental margin along the southern edge of the Congo-BaNy (combined Bangweulu Block-Nyika Subdomain) Craton. The first phase of the Irumide orogeny, resulting from arc accretion of the Irumide and South Irumide Domains to the Congo Craton, is dated at 1069 ± 9 Ma by local syntectonic anatectic melting in the suture between them. This was followed by closure of the Irumide Ocean and docking of the Proto-Kalahari craton from the south at c. 1045 Ma, which represents the main Irumide tectono-metamorphic event. Voluminous, syn-collision magmatism at c. 1040 Ma resulted from melting and assimilation of Ubendian-age continental crust from the Irumide Domain mixed with mantle-derived juvenile crust of the South Irumide Domain. Structural observations show that the Irumide Domain is sandwiched between South Irumide Domain rocks at the base of the tectonic pile and Congo Craton on top. This suggests that N-directed subduction of the Irumide Ocean beneath the Irumide Domain was followed by south-directed nappe transport during the collision phase. Our revised model of the Irumide Orogeny suggests that the main crustal architecture of southern Africa was established at the end of the Mesoproterozoic and is not just the result of the Neoproterozoic Pan-African, East African orogeny as advanced by some researchers
Biofouling in milli-labyrinth channels of drip irrigation systems using reclaimed wastewater: A review of optical methods and numerical modelling
No full textInternational audienceDrip irrigation systems are known for their high water-use efficiency due to the combination of using milli-labyrinth channels to optimise flow distribution and reusing reclaimed wastewater. However, clogging andbiofouling remain significant challenges that affect system performance and lifespan. This review provides acomprehensive overview of biofouling in drip irrigation systems, with a focus on how hydrodynamic conditionsand nutrient availability in reclaimed wastewater influence the attachment, growth, detachment, and decayof biofilm. The ability of advanced optical techniques, including particle tracking velocimetry, industrialcomputed tomography, and optical coherence tomography to visualise, measure, and analyse biofoulingprocesses in drip irrigation systems is discussed, along with their strengths and limitations. Additionally, theability of current biofilm modelling approaches, including both continuum and discrete methods, to simulatenutrient transport, microbial activity, and biofilm–fluid interactions are discussed. By combining insights fromexperimental data and computational models, this review also identifies key research gaps and presents a newframework for applying biofilm modelling to drip irrigation systems. Future research directions are suggestedto improve our understanding of drip irrigation biofouling and to predict it, to optimise emitter design, andincrease the overall reliability and sustainability of drip irrigation system
Life cycle inventories of global metal and mineral supply chains: a comprehensive data review, analysis and processing
No full textInternational audienceReliable life cycle inventory (LCI) data are key to consistent life cycle assessment (LCA) results. This study provides a comprehensive and up-to-date overview of existing public LCI data related to metals and minerals production. It aims to deliver LCI models representing current supply chains and markets. For that purpose, this study conducts an in-depth analysis (including data quality) of 285 LCI datasets drawn from 130 different LCA studies related to metals and minerals. Following a selection process and a harmonised data compilation, processing and modelling approach, 220 individual LCI datasets were developed, covering 53 metal and mineral elements and distinguishing 163 production routes differentiated from geographical, geological, technological or material perspectives. Finally, these LCI datasets were gathered into market datasets, depicting global supply mixes. Elements such as germanium or manganese showed a limited market coverage, contrary to others such as lithium or aluminium.Available in open access, the high-resolution LCI datasets here developed offer key perspectives for a better modelling of metal and mineral supply chains in LCA, in turn contributing to higher quality LCAs of downstream product systems utilising these materials. At the same time, this study reveals several data gaps, paving the way for further data improvement
Neon Isotopes in Individual Vesicles of Icelandic Basaltic Glasses: Insights into the Origin of Light Volatile Elements on Earth
No full textInternational audienceThe origin of Earth's volatile elements remains a topic of debate due to the diverse sources within the solar system. Noble gases, owing to their chemical inertness, serve as powerful tracers for investigating planetary formation and mantle evolution. Noble gas isotopic studies suggest the existence of a preserved, relatively undegassed mantle reservoir, which is tapped by deep-rooted mantle plumes, such as those beneath the Galápagos, Hawaii, and Iceland. We present the first measurements of neon isotopic ratios in individual vesicles from a subglacially erupted basalt from Iceland. This method allows for the measurement of noble gas isotopes free from atmospheric contamination. Through statistical analyses of neon isotopic ratios in individual vesicles, we derive the isotopic composition for Ne of the Iceland mantle to be 12.63 ± 0.14 for the 20Ne/22Ne ratio. This value is in excellent agreement with the Galápagos mantle source and the signature expected for implanted solar wind, and lower than that of the value expected for the dissolution of a primordial atmosphere in the magma ocean. These results suggest a dominant role for solar wind implantation in accounting for Earth's mantle neon isotopic signature, and therefore as the source of light volatile elements. However, neither the implantation nor the nebular dissolution model is entirely satisfactory to explain all observations. Both models are not necessarily mutually exclusive, and more work should be conducted to tackle this long-standing issue
Governing by promises. Water scarcity and rural hegemony in Morocco
No full textSource Agritrop Cirad (https://agritrop.cirad.fr/616979/)International audienceOver the last decade, an important field of inquiry has emerged around the notion of promissory legitimation. It focuses less on the fulfillment of collective promises than on their production and reception. This paper aims, first, to foreground its relevance for – critical- policy studies, by highlighting the decisive role that promises can play in the (re)production of hegemony. Second, and more specifically, it seeks to identify some practices of promise adjustment: the everyday strategies by which governing actors adapt, modify and re-assert their promises when their credibility is under stress, in order to reproduce the hegemony of the same groups in society. I explore these practices in the case of an irrigation megaproject in Morocco, where a developmentalist promise is proving insufficient to defuse tensions surrounding future water access. I show that a key adjustment mechanism is to add new promises on top of the first one – in this case, a clientelist promise and a laissez-faire promise. The coexistence of different promises, however, displays the same chronic contradictions as policy in general, with the same attendant limitations in the hegemony it attempts to uphold